Disclosure of Invention
Aiming at the defect of over-low fracture toughness of ultra-high temperature ablation-resistant ceramic in the prior art, the invention aims to provide a tungsten mesh toughened hafnium carbon nitride-based cermet (HfC) with excellent thermal shock resistance and excellent ablation resistance and a preparation method thereofxNy) The ceramic material is suitable for the ultra-high temperature ablation protection at 3000 ℃, the cermet can still keep complete after long-time ablation, brittle fracture does not occur, and the ceramic material has a stable antioxidant protection structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a tungsten mesh toughened hafnium carbon nitride-based cermet, which consists of a hafnium carbon nitride matrix and tungsten meshes distributed in the hafnium carbon nitride matrix at intervals.
The invention adopts multilayer tungsten nets to toughen HfCxNy ceramics, and tungsten is used as metal with the highest melting point, so that the ceramic material has the characteristics of high strength, high melting point, good plasticity, strong impact toughness and the like; in addition, the inventor finds that the hafnium carbonitride and the metal tungsten have excellent chemical compatibility and thermal matching, and after the tungsten mesh with multiple layers of evenly distributed intervals is added, the fracture toughness and the bending strength of the hafnium carbonitride at high temperature can be effectively improved, so that the reinforced and toughened ultrahigh-melting-point hafnium carbonitride-based composite material is formed. When the high-temperature thermal stress acts and the crack is expanded to the tungsten net, the tensile stress borne by deflection is reduced, the expansion path is prolonged, and the fracture energy of the material is increased. When the shear stress reaches the initial debonding stress of the interface of the tungsten mesh and the solid solution matrix, namely the interface shear strength, debonding occurs, on one hand, the interfacial friction force is overcome to do work, and the fracture energy is increased; on the other hand, the stress at the crack tip is relaxed, and the crack propagation is delayed. And the regularly arranged network-shaped structures can play the effects of bridging cracks and inhibiting crack propagation.
In a preferred embodiment, in the hafnium carbonitride matrix, in terms of mass ratio, C: n-1-7: 1; preferably 1-3: 1.
When the mass ratio of carbon to nitrogen in the hafnium carbonitride matrix is within the above range, the tungsten mesh toughened hafnium carbonitride-based cermet has the most excellent ablation resistance.
In a preferable scheme, the number of the tungsten mesh layers is 3-8, preferably 3-6, and further preferably 4-6, each tungsten mesh layer is composed of a piece of tungsten mesh, the tungsten mesh layers are uniformly distributed in the hafnium carbonitride matrix at intervals, and the thickness of the tungsten mesh toughened hafnium carbonitride-based cermet is 3-6 mm.
In a preferred embodiment, the mesh number of the tungsten mesh is 80-300 meshes, preferably 100-200 meshes.
In the invention, the mesh number of the tungsten mesh is the mesh number of the tungsten mesh, when the mesh number of the tungsten mesh is controlled to be within the range, the tungsten mesh toughened hafnium carbon nitride based cermet has excellent toughness, and the tungsten mesh toughened hafnium carbon nitride based cermet has excellent ablation performance, if the mesh number is too small, the toughness is affected, and if the mesh number is too large, the ablation performance is affected.
The invention relates to a preparation method of tungsten mesh toughened hafnium carbonitride based metal ceramic, which comprises the following steps:
mixing HfC powder, HfN powder, carbon powder and carbon nitride powder, ball-milling, drying and sieving to obtain mixed powder; in the mixed powder, the weight ratio of HfC powder: and (3) alternately laminating and laying the mixed powder and the tungsten mesh in a mold to obtain a to-be-sintered body, and performing discharge plasma sintering on the to-be-sintered body to obtain the tungsten mesh toughened hafnium carbonitride-based metal ceramic.
In a preferred embodiment, in the mixed powder, by mass ratio, the HfC powder: HfN powder 1-3: 1; preferably 1.5-3: 1.
In a preferred embodiment, the purity of the HfC powder and the HfN powder are both greater than 99.9%, and the particle size of the HfC powder and the HfN powder are both micron-sized or nanometer-sized.
In a preferable scheme, the mass fraction of the carbon powder in the mixed powder is less than or equal to 8.0 wt%, and is preferably 3 wt% -wt 5%.
In a preferable scheme, the mass fraction of the carbon nitride powder in the mixed powder is less than or equal to 5.0 wt%, and preferably 4 wt% -5 wt%.
In the invention, the ball milling equipment is not limited, preferably a high-energy planetary ball mill, the ball milling mode is preferably wet ball milling, and the ball milling medium is ethanol solution.
Preferably, the ball milling rotation speed is 200-: 1.
preferably, the drying time is 8-12h, the drying temperature is 50-150 ℃, and the drying is carried out in a vacuum environment; drying, sieving with 325 mesh sieve, and collecting the undersize product to obtain mixed powder. The obtained mixed powder is hermetically stored in an air-tight manner.
According to the preferable scheme, the mixed powder and the tungsten net are alternately and uniformly stacked and laid in the die, the number of the tungsten net layers is 3-8, preferably 3-6, and further preferably 4-6, and the same tungsten net layer consists of one tungsten net.
The mixed powder and the tungsten net are alternately stacked and laid on the die, namely: the mixed powder is divided into a plurality of equal parts, then a layer of mixed powder is paved in the graphite mould stuffing, then a layer of tungsten net is paved, then a layer of mixed powder is paved, and in this way, a plurality of layers are paved repeatedly.
In the actual operation process, the tungsten net is subjected to ethanol ultrasonic treatment and then has a smooth and clean surface.
In a preferred embodiment, the mesh number of the tungsten mesh is 80-300 meshes, preferably 100-200 meshes.
Preferably, the thickness of the body to be sintered is 6-12mm, preferably 8-10 mm. In the invention, the sintered body is subjected to pressure sintering in SPS equipment, and the thickness of the sintered compact cermet is 3-6 mm.
In a preferable scheme, the spark plasma sintering is carried out in a vacuum environment, and the vacuum degree is less than 5 Pa; the sintering procedure is as follows: heating to 2400 ℃ at a heating rate of 50-150 ℃/min, preserving heat for 5-30min, and cooling at a cooling rate of 120 ℃/min of 100-150 ℃/min after heat preservation is finished, wherein the sintering pressure is 20-60 Mpa.
Further preferably, the sintering procedure is: heating to 1900-2100 ℃ at the temperature-raising rate of 120 ℃/min and 100-20 min, and cooling at the temperature-lowering rate of 120 ℃/min and 100-40 MPa after the heat preservation is finished.
And after sintering, demolding the sintered body to obtain the tungsten mesh toughened hafnium carbonitride-based metal ceramic.
Principles and advantages
The invention adopts multilayer tungsten net to toughen HfCxNy ceramics for the first time, and tungsten is used as metal with the highest melting point, thus having the characteristics of high strength, high melting point, good plasticity, strong impact toughness and the like; in addition, the inventor finds that the hafnium carbonitride and the metal tungsten have excellent chemical compatibility and thermal matching, and after the tungsten mesh with multiple layers of evenly distributed intervals is added, the fracture toughness and the bending strength of the hafnium carbonitride at high temperature can be effectively improved, so that the reinforced and toughened ultrahigh-melting-point hafnium carbonitride-based composite material is formed. When the high-temperature thermal stress acts and the crack is expanded to the tungsten net, the tensile stress borne by deflection is reduced, the expansion path is prolonged, and the fracture energy of the material is increased. When the shear stress reaches the initial debonding stress of the interface of the tungsten mesh and the solid solution matrix, namely the interface shear strength, debonding occurs, on one hand, the interfacial friction force is overcome to do work, and the fracture energy is increased; on the other hand, the stress at the crack tip is relaxed, and the crack propagation is delayed. And the regularly arranged network-shaped structures can play the effects of bridging cracks and inhibiting crack propagation.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) the preparation process flow is simple and easy to implement, and the preparation period is short;
(2) the prepared sample has good thermal shock resistance. After ablation for 300s at 3000 ℃ in an oxyacetylene flame environment, the metal ceramic is still completely stored without brittle fracture;
(3) the prepared sample has good ablation resistance. The mass ablation rate and the line ablation rate after the material is ablated for 300s in an oxyacetylene flame environment at 3000 ℃ are only 3.67 multiplied by 10-4mg/s、2.34×10-3mm/s。
Detailed Description
Example 1
Mixing HfC powder, HfN powder, carbon powder and carbon nitride powder, then ball-milling for 10h on a planetary ball mill with the ball-milling medium of ethanol solution at the rotating speed of 300r/min and the ball-material ratio of 10:1, then placing the mixture in a drying oven at 60 ℃ for drying for 8 hours, and sieving to obtain mixed powder. Wherein the purity of each raw material powder is more than 99.9 percent, the average particle size of the powder is 1um, and the mass ratio of HfC powder to HfN powder in the mixed powder is 3: 2; the mass fraction of the carbon powder in the mixed powder is 5%, and the mass fraction of the carbon nitride in the mixed powder is 5%.
Selecting a 100-mesh tungsten net, cleaning the tungsten net with the purity of more than 99.9 percent by using ethanol ultrasound for 30 minutes, drying the tungsten net, taking the tungsten net out, and cutting the tungsten net into the diameter of a grinding tool. And then, uniformly and alternately placing the mixed powder and the tungsten net in a graphite mold, arranging the mixed powder and the tungsten net in 5 layers, performing discharge plasma sintering when the thickness of a sintered body is 10mm, wherein the vacuum degree in the furnace is less than 5Pa, heating to 2000 ℃ at the heating rate of 100 ℃/min, keeping the temperature for 15 minutes, keeping the pressure at 40Mpa, and then cooling to room temperature at the cooling rate of 100 ℃/min. Obtaining the multilayer network toughened carbon-nitride-hafnium-based metal ceramic with the thickness of 4.79mm after demoulding treatment. The brittle fracture does not occur after the sample is ablated for 300s under the oxyacetylene flame environment at the temperature of 3000 ℃, the sample is kept complete, and the mass ablation rate is only 3.67 multiplied by 10-4mg/s, line ablation rate of 2.34X 10-3mm/s。
Example 2
Mixing HfC powder, HfN powder, carbon powder and nitrided carbon powder, then ball-milling for 12h on a planetary ball mill, wherein the ball-milling medium is ethanol solution, the rotating speed is 200r/min, the ball-to-material ratio is 8:1, then placing the mixture in a drying oven at 50 ℃ for drying for 10 hours, and sieving to obtain mixed powder, wherein the purity of each raw material powder is more than 99.9%, the average particle size of the powder is 1um, and the mass ratio of HfC powder to HfN powder in the mixed powder is 2: 1; the mass fraction of the carbon powder in the mixed powder is 4%, and the mass fraction of the carbon nitride in the mixed powder is 4%.
Selecting a 80-mesh tungsten net, cleaning the tungsten net with the purity of more than 99.9 percent by using ethanol ultrasound for 20 minutes, drying the tungsten net, taking the tungsten net out, and cutting the tungsten net into the diameter of a grinding tool. And then uniformly and alternately placing the mixed powder and the tungsten net in a graphite mold, wherein the total thickness of the tungsten net is four layers, when the thickness of a sintered body is 8mm, carrying out discharge plasma sintering, wherein the vacuum degree in the furnace is less than 5Pa, heating to 2100 ℃ at the heating rate of 120 ℃/min, keeping the temperature for 15 minutes, keeping the pressure at 35Mpa, and then cooling to the room temperature at the cooling rate of 100 ℃/min. Obtaining the multilayer tungsten mesh toughened carbon-hafnium nitride-based metal ceramic with the thickness of 3.84mm after demoulding treatment. The brittle fracture does not occur after the material is ablated for 180s under the oxyacetylene flame environment at 3000 ℃, the sample is kept complete, and the mass ablation rate is only 4.53 multiplied by 10-4mg/s, line ablation rate of 3.97X 10-3mm/s。
Example 3
Mixing HfC powder, HfN powder, carbon powder and carbon nitride powder, then ball-milling for 12h on a planetary ball mill with an ethanol solution as a ball-milling medium at a rotation speed of 200r/min and a ball-to-material ratio of 9:1, then placing in a drying oven at 70 ℃ for drying for 10 hours, and sieving to obtain mixed powder. Wherein the purity of each raw material powder is more than 99.9 percent, the average particle size of the powder is 1um, and the mass ratio of HfC powder to HfN powder in the mixed powder is 3: 1; the mass fraction of the carbon powder in the mixed powder is 3%, and the mass fraction of the carbon nitride in the mixed powder is 4%.
Selecting a 120-mesh tungsten net, performing ultrasonic treatment on the tungsten net with the purity of more than 99.9 percent by using ethanol, and drying the tungsten net. Cutting into the diameter of the grinding tool, then uniformly and alternately placing the mixed powder and the tungsten net in a graphite die to form six layers of tungsten netsThe thickness of the sintered body is 12mm, the discharge plasma sintering is carried out, the vacuum degree in the furnace is less than 5Pa, the temperature is raised to 1900 ℃ at the heating rate of 120 ℃/min, the temperature is kept for 20 minutes, the pressure is 40Mpa, and then the temperature is cooled to the room temperature at the cooling rate of 100 ℃/min. And obtaining the multilayer tungsten mesh toughened hafnium carbonitride based cermet after demolding treatment. The brittle fracture does not occur after the sample is ablated for 300s under the oxyacetylene flame environment at 3000 ℃, the sample is kept complete, and the mass ablation rate is only 5.38 multiplied by 10-4mg/s, line ablation rate of 4.56X 10-3mm/s。
Comparative example 1
The tungsten mesh is not added for toughening, other conditions are the same as those of the example 2, and the brittle fracture occurs after the ablation is carried out for 180s in the oxyacetylene flame environment at the temperature of 3000 ℃.
Comparative example 2
Only one tungsten mesh was added, and other conditions were the same as in example 2, and brittle fracture occurred after ablation for 180 seconds in an oxyacetylene flame environment at 3000 ℃.
Comparative example 3
Adding a 30-mesh tungsten net for toughening, wherein other conditions are the same as those of the example 2, and the brittle fracture occurs after the material is ablated for 180s in an oxyacetylene flame environment at 3000 ℃.
Comparative example 4
Ball-milling HfC and HfN powder on a planetary ball mill according to the mass ratio of 8:1, wherein the other conditions are the same as those of the example 2, and the mass ablation rate and the line ablation rate are greatly increased after ablation is carried out for 180s under the oxyacetylene flame environment at 3000 ℃, and are respectively 7.83 multiplied by 10-2mg/s, line ablation rate of 6.27X 10-1mm/s。